This invention relates generally to a photographic film cassette, or cartridge, for use in a camera of the self-developing type in which photographic film exposed within the camera is developed by a process involving diffusion transfer upon being withdrawn from the camera. More particularly, the invention relates to a photographic film cassette wherein a plurality of photographic film units are arranged in a flat configuration so as to be exposed within a photographic apparatus.
Cassettes which are capable of retaining instant, self-developing film units are well known in the art. Such cassettes are typically flat, elongated containers having an exposure opening in one wall through which light from the subject or scene being photographed can be focused and an exit opening formed in another wall through which an exposed film unit can be withdrawn from the container for photographic processing subsequent to having been exposed within the photographic apparatus.
Diffusion transfer photographic self-developing film units include a photosensitive, or negative, element and an image-receiving, or positive, element in the form of thin, sheet-like members. In one embodiment, commonly referred to as "peel-apart" the photosensitive and image-receiving elements are designed to be separated from each other after exposure and photographic processing have been effected. In another embodiment, commonly referred to as "integral", the photosensitive and image-receiving elements are retained together after photoexposure and photographic processing have been carried out. Both types of instant, self-developing film units have been described extensively in the literature and are well known to those skilled in the art.
Generally speaking, a plurality of self-developing film units are arranged in stacked relationship within the cassette and typically the photosensitive element of each successive film unit is urged into position at the focal plane of the photographic apparatus by some pressure-applying means which may be within the cassette or partially outside the cassette. In the case of a peel-apart film unit the respective photosensitive and image-receiving elements can be arranged in superposed relationship such that the photosensitive layer(s) and the image-receiving layer of each film unit face in the direction of the exposure opening in the cassette. The cassette, as noted previously, may also include pressure-applying means, which may include a plate located between the respective elements to urge the photosensitive element into a phase which coincides with the focal plane of the photographic apparatus. Typically, in the peel-apart type, the photosensitive and image-receiving elements are interconnected by web means which cooperate with the pressure-applying means so the image-receiving element can be moved relative to the cassette, after exposure of the photosensitive element, until it is positioned in registration with, and adjacent to, the exposed photosensitive element with the photosensitive layer(s) of the photosensitive element adjacent to the image-receiving layer of the image-receiving element. In this registered relationship the introduction of a photographic processing composition between the photosensitive and image-receiving elements initiates photographic development and results in image-forming materials being transferred by diffusion from the photosensitive element to the image-receiving element. The introduction of the processing composition can take place when the respective elements, in registered superposed relationship, are moved longitudinally through the exit opening of the cassette and through pressure-applying means, typically a pair of rollers, mounted within the photographic apparatus. Preferably, the processing composition is contained within a rupturable fluid-holding container, commonly referred to as a "pod" which is attached to the film unit. Movement of the film unit through the pressure-applying means causes the pod to rupture and the fluid processing composition to be distributed between the elements. Upon passage of the film unit through the pressure-applying means and the resultant spreading of the processing composition, the diffusion of image-forming materials to the positive element preferably takes place outside the photographic apparatus.
Various types of self-developing film units are available commercially and each is intended to be used in conjunction with particular photographic apparatus. The characteristics of the appropriate photographic apparatus, in conjunction with the film units provide the results desired. Thus, it is important that a photographic film cassette containing self-developing film units designed to be used with particular photographic apparatus not be inserted into, and exposed and processed with, different photographic apparatus. It is therefore an object of the invention to provide a photographic film cassette which can only be inserted in photographic apparatus specifically designed to accept the cassette.